Background Recently, ultraviolet (UV) A1 phototherapy has been suggested as an effective treatment for localized scleroderma (LS); however, the optimal dose of UVA1 still has not been determined. Objective We aimed to evaluate the therapeutic effectiveness of medium-dose (30 J/cm(2)) UVA1 phototherapy and to show that 13 MHz ultrasound is a valuable tool for assessing the results of UVA1 phototherapy in LS. Methods Thirty-five patients with LS were treated with medium-dose (30 J/cm(2)) UVA1. In total, 30-45 treatments and 900-1350 J/cm(2) cumulative UVA1 doses were evaluated by clinical scoring in all patients. In 14 patients, skin thickness was also determined by 13 MHz ultrasound examination. Results In all patients, medium-dose UVA1 therapy softened sclerotic plaques, and marked clinical improvement was observed in 29 of 35 (82. 85%) patients. Ultrasound measurements showed that skin thickness was significantly reduced. No side effects were observed during or after treatment. Conclusion Medium-dose UVA1 phototherapy is a highly effective, safe, and well-tolerated therapeutic modality for treatment of all types of LS. A 13 MHz ultrasound probe may be used for evaluating UVA1 phototherapy results.